Rectifier system



April 5, 1938- i J. R. POWER 2,113,220

Y `RECH-PIER. SYSTEM `Filed June. l, 1936 LE v n /26 ski l 32E- j u l/5`y29 N u v @e /4 24 2a fao 5 n -rff /6 /7 V l i -25 27 /fo j 9 /a I 4 2A'AYMY .y C cr= 3a 36 35 V2 4/ 3'7 t l I I RJ uw o /NL/.EN IOR J. R.POWER Z yx ATTORNEY Patented Apr. 5,

l UNITED STATES PATENT OFFICE Bell Telephone laboratories, Incorpora NewYork, N. Y., a corporation oi' New York ted,

Application June l, 1936, Serial No. 82,882

This invention relates to rectiiier'systems and particularly toregulated rectiiler systems.

One object of the invention is to provide a rectifier system with agas-illled rectier device having alternating and direct potential biasimpressed on the control grid oi the device that shall vary the directpotential bias to maintain the rectiiled potential substantiallyconstant.

. Another object o! the invention is to provide a rectiiler systemhaving a gas-filled rectiiler device governed by a control grid andconnected to an alternating current supply circuit that shall beconnected to a load circuit by a illter serving to prevent sharp changesin the rectiiled voltage while preventing delay in the rectifier cut-ol.

Another object of the invention is to provide a rectifier system with athree-element gas-nlled rectifier governed by alternating and directpotential impressed on the grid that shall have the filament oftherectifier heated by alternating current with the filament terminalspolarized to add the potential drop across the lament to the criticalgrid voltage.

A further object of the invention is to provide a rectiiler systemhaving a gas-lilled rectifier device connected between an alternatingcurrent supply circuit and a direct current load circuit and direct andalternating potential bias impressed on the control grid of the devicethat l shall vary the direct potential bias in an improved manner tomaintain the rectified voltage substantially constant and that shallvary lthe level at which the rectiiled voltage is maintained constant inan improved manner.

In xectier systems it is very desirable an citen essential to maintainthe rectified voltage substantially constant. The load circuit voltagemust be maintained constant irrespective of changes inload on the loadcircuit or of changes in voltage on the supply circuit. Furthermore, therectied voltage must not only be maintained constant but the level atwhich the load circuit voltage is maintained constant should be variedat will.

In a rectier system constructed in accordance with the invention twogas-illled space discharge devices are connected in opposition betweenan alternating current supply circuit and a direct current load circuitto supply full wave rectified current to the load circuit. The termgas-nlled space discharge device is intended to include vapor lleddevices. 'I'he grids oi.' the gas-filled devices not only havealternating potential bias impressed on them, but also have a directpotential bias impressed on them for controlling the voltage oi' theload circuit. 'Ihe alternating current bias impressed upon the grids ofthe rectiiler devices lags approximately 90 degrees behind,

the potential impressed on the plates. The phase relation between thepotential impressed upon the plate of each tube and the alternatingpotential impressed on the grid is maintained Substantially constant.

A tilter which is interposed between the gasillled devices and the loadcircuit is designed in a manner to insure against holdover in the cutoiloi the gas-filled devices and to insure against sudden change in theload circuit voltage. In order to prevent hangover in the cut-ofl'o! thegas-filled devices the reactance ci the series inductance element in theinput section oi' the nlter is made relatively small. In order toprevent sudden change in the voltage of the load circuit the shuntcapacity element in the output of the lter is made relatively large.Unless the series inductance element in the input section of the nlteris made relatively small, it is dimcult to obtain cut-oi! by thegas-nlled devices. The hangover period may be a substantial portion oithe conducting period at very light loads. The output capacity elementof very large sine may under many conditions be replaced by a iloatingbattery ii so desired.

A resistance comprising three sections is connected across the loadcircuit. A regulator space discharge device has the grid circuit thereofconnected across one section oi' said resistance. Plate potential forthe regulator device is provided by the drop across two sections of saidresistance. A source o! grid bias is connected to the grid circuit ofthe regulator device to provide a bias in opposition to the drop acrossthe resistance section connected to the regulator grid circuit. In theregulating range the potential drop across the resistance section isslightly smaller than the potential supplied in opposition thereto. Theplate circuit oi the regulator tube is coupled to the grid circuits ofthe rectifier devices in order to supply a direct potential bias for socontrolling the rectiiler devices as to maintain the rectied voltagesubstantially constant.

A third section oi' the resistance connected.

across Ythe load circuit is made variable in order to control the levelat which the load circuit voltage is maintained constant. A variableautotransformer is inserted in the alternating current supply circuitahead of the rectifier devices for controlling the potential impressedon the plate of the rectiiler devices. The auto-transformer is varied inorder to insure that the voltage impressed on the plates of therectifier devices effects efficient rectification under optimumconditions. Preferably the adjustment of the third section of theresistance across the load circuit and the auto-transformer in thesupply circuit are effected simultaneously by the same means so that achange in the load circuit conditions is effected at the same time thata change in the potential impressed on the plates of the rectifierstakes place.

The filaments of the two gas-filled rectifier devices are connected inseries to the alternating current supply circuit in order to provide amoderate gain in the reliability of control of the regulator. Theterminals of the filaments opposite to the common grid return terminalare polarized 4oppositely to the polarization of the associated plates.'I'he series connection of the filaments and polarizing them as aboveset forth causes a. shift in the critical grid voltage measured betweenthe grid and the grid return connection according to the potential dropacross the filaments. An increase in the critical grid voltage permitsan increase in the magnitude of the alternating potential bias which isimpressed on the grids of the' gas-filled rectifier devices. Increasingthe alternating potential bias on the grig of the rectifier devicesincreases the angle of intersection of the grid bias with the criticalvoltage as will be pointed out in detail.

In the accompanying drawing Fig. 1 is a diagrammatic view of a regulatorsystem constructed in accordance with the invention;

Fig. 2 is a set of curves showing the plate voltage, the critical gridvoltage, and the grid bias for a conducting half-cycle of a rectifierdevice;

Fig. 3 is a set of curves of critical grid voltage and grid bias showingthe effect of polarizing the filament terminal opposite to the gridreturn terminal oppositely to the polarity of the plate.

Referring to Fig. 1 of the drawing two gasfilled space dischargerectifiers I and 2 are connected to alternating current supplyconductors 3 and 4 by means of a transformer 5 and an auto-transformer6. The transformer 5 comprises a primary winding I. and two secondarywindings 8 and 9. A load circuit comprising conductors I0 and II isconnected by a. filter I2' to the rectifier devices l and 2 to besupplied with full wave rectified current from the supply conductors 3and 4.

The rectifier device I comprises an anode I3, a grid I4 and a filamentI5. The rectifier device 2 comprises an anode I6, grid I'I and afilament I8. A transformer I9 which is connected to the alternatingcurrent supply conductors 3 and 4 by a switch 20 supplies heatingcurrent to the filaments I5 and I8. The transformer I9 comprises primarywinding 2I, secondary winding 22 and secondary winding 23. Secondarywinding 22 is connected to the series connected filaments I5 and I8 ofthe rectifier devices I and 2. The connection is so made that referredto the 'grid and plate return connection the terminal 24 of the filamentI5 is polarized oppositely to the polarization of the anode I3, and theterminal 25 of the filament I8 is polarized oppositely tolthepolarization of the anode I6.v

The polarizing of the terminals of the filaments as above set forthserves to increase the critical external grid voltage according to thepotential drop across the filaments.

The grids I4 and I'I of the rectifier devices I and 2 are connectedthrough resistance elements 25 and 21 to a divided secondary winding 28of a transformer 29. The resistance elements 26 and 21 serve to opposethe fiow of current through the grid circuits. The primary winding 30 ofthe transformer 29 is connected through a condenser 9I to a section ofthe secondary winding 23. The transformer 29 and the secondary winding23 of the transformer I9 serve to impress alternating potential bias onthe grids I4 and II from the supply conductors 3 and 4. The condenser 3|serves to effect a lag of approximately degrees in the alternatingpotential impressed on the grids I4 and Il with respect to thealternating potential impressed on the anodes I3 and I6. The phaserelation between the alternating potential impressed on the grids I4 andII with respect-to the alternating potential impressed on the anodes I3and I6 is assumed to remain substantially constant. A switch member 32is provided for connecting one terminal of the auto-transformer 6 to thealternating current supply conductor 3. In operation of the rectifiersysteml the switch 20 should be closed for about 10 seconds before theswitch 32 is closed.

A three-element space discharge device 33 is provided for impressing adirect potential bias on the grids I4 and II of the rectifier devices Iand 2 according to the voltage across the load conductors III and II.The rectifier device 33 comprises an anode 34, a grid 35 and a cathode36 which is heated by filament 31. The filament 31 is heated by acurrent supplied from the secondary winding 23 of the transformer I9. Aresistance 38 which is connected across the load conductors II) and IIis divided into sections RI, R2 and R3. The grid circuit for theregulator device 33 is connected across the resistance section R2. Inthis grid circuit is provided a battery 39, the potential of whichopposes the potential drop across the resistance section R2. Anodepotential for the regulator device 33 is provided by the potential dropacross the resistance sections RI and R2. A-coupling resistance R4 inthe anode circuit of the regulator device 33 serves to impress thedirect potential bias on the grids I4 and II of the rectifier devices Iand 2. The bias impressed on the grid 35 of the regulator device 33 isthe difference between the voltage of the battery 39 and the potentialdrop across the resistance section R2. In the regulating range thepotential drop across the resistance section R2 is slightly less thanthe voltage of the battery 39. In the regulating range the currentthrough the resistance section R2 and therefore through the entireresistance 38 must be maintained at approximately fixed value. 'Ihe loadcircuit voltage at which the regulator operates is therefore equal tothis fixed current times the total resistance of a resistance 38. Byreason of this fact adjustment of the level at which the load circuitvoltage is maintained constant is controlled by varying the resistancesection R3. The resistance section R3 is varied by means of a contactarm 4I.

During operation of the regulator device 33 an increase in the loadcircuit voltage will increase the potential drop across the resistancesection R2 and thereby decrease the negative grid bias on the regulatordevice 33. This action will increase the current fiow through the deviceand increase the current flow throughthe coupling resistance R4. Anincrease in the current flow through the coupling resistance R4increases the direct negative bias on the grids I4 and I'I of therectifier devices I and 2. An increase in the direct potential biasretards the triggering off point for the rectifier devices I and 2 willbe explained more in detail when reference is made to Fig. 2 ofthedrawing. Delaying the triggering of! point of the rectifier devices Iand 2 serves to reduce the voltage on the load conductors III and II.

The filter I2 is provided with a series inductance LI, a seriesinductance L2, a shunt capacity impedance. CI and a shunt capacityimpedance C2. The inductance LI in the input section of the filter ismade relatively small in order to prevent delay in the cutoffpoints ofthe rectifier devices I and 2. In generall the reactance of' theinductance LI at twice the frequency of the supplycircuit current shouldnot be more than three to five times the reactance of the shunt capacityCI. It is necessary to prevent delay in the extinguishing of therectifier devices I and 2 if lower load limits of stable operation areto be provided.

Any regulator device tends to hunt or oscillate When the precision ofregulation is increased beyond a. critical value. predominant factorscontrolling this critical value are the abruptness of the change in thefunction being regulated, in the present case the output voltage, andthe delay in its correction. The delay is due to the time required totransmita signal through the regulating circuits plus the time requiredfor the source to be corrected. In the present circuit the signal istransmitted through the regulator instantaneously. Ihere is a delaywhich may reach a half cycle in the rectifier device response and afurther delay in transmitting the correction through the filter.Inasmuch as the filter delay is usually determined by requirementscovering the output noise level, the circuit has minimum practical timedelay.k An increase in the stability of operation is `therefore largelydependent upon a reduction of the abruptness of output voltage changes.This is accomplished and a greater precision thereby made permissible bythe use of a. large shunting condenser C2.

The auto-transformer 6 is controlled by a contact arm 42 to govern thepotential impressed on the anodes I3 and I6 of the rectifier devices Iand 2. 'Ihe transformer 6 is adjusted so as to operate the rectifierdevices I and 2 enlciently and to insure operation under optimumconditions. Preferably, the contact arm 42, which controls theauto-transformer 6 and the contact arm 4I, are mechanically yconnectedso as to be operated simultaneously. It is, of course, apparent that achange in the resistance section R3 with resulting change in loadcircuit voltage requires a correl lsponding change in theauto-transformer 8.

If the voltage across the load conductors I0 and II tends to increase,the voltage drop across the resistance section R2 tends to increase.This n lowers the negative bias on the grid 35 of the regulator device33. An increased current 'flows through the regulator device 33 toincrease the potential drop across the coupling resistance R4. Anincrease in the potential drop across the coupling resistance R4increases the negative direct potential bias impressed on the grids I4and I'I of the rectifier devices I and 2. An increase in the directpotential bias retards the triggering ofi point of the rectifier devicesI and 2. This, in turn, reduces the rectified voltage supplied to theload conductors I0 and I I. An opposite effect takes place if thevoltage on the load conductors II) and II tends to fall below normalvalue.

The regulator device 33 will operate to maintain a constant potentialdrop across the resistance section R2` In maintaining a constantpotcntial drop across the resistance section R2 the voltage of the loadcircuit conductors III and II will be maintained constant. In view ofthe above fact it is apparent that a change in the resistance section R3must cause a change in the level at which the load circuit voltage ismaintained constant. This is apparent because the potential drop acrossthe resistance section R2 is held constant and therefore the level atwhich the load circuit voltage is held constant must change if a changeis made in the resistance section R3.

Referring to Fig. 2 of the drawing a set of curves are shown with timeor electrical degrees as abscissae and plate volts and grid volts asordinates. The curves represent the operation for a conductinghalf-cycle of one rectifier device. The curve 44 may be considered theplate voltage of one rectifier device. The curve 45 represents thecritical grid voltage for one rectifier device. By critical grid voltageis meant the voltage between the grid and the grid return connections atwhich the rectifier device may be ignited. The curves 46, 41 and 48represent grid biasing currents with different amounts of directpotential bias. At the point a. where the grid bias curve 46 intersectsthe critical grid voltage curve 45 the rectifier device will trigger ofito permit current flow therethrough. If negative direct current bias isadded to the rectifier device a curve as shown by curve 41 is producedwhich intersects the critical grid voltage curve at point b. Therectifier device under such condition will ignite and start to conductcurrent at a much later time as shown by the distance on the abscissaebetween points a and b. If more direct potential bias is added to thegrid of the rectifier device a curve such as 48 may be provided whichintersects the critical voltage vcurve at a point c. The point c willthen indicate the time of ignition for the rectifier tube.

Referring to Fig. 3 of the drawing, curves are drawn to show the effectof connecting the filaments I5 and I8 of the rectifier devices I and 2in series and polarizing the terminals of the filaments in the mannerbefore set forth. 'I'he terminals 24 of the filamentA I5 must bepolarized oppositely to the lpolarization of the anode I3 and thefilament terminal 25 must be polarized oppositely to the polarization ofthe anode IS. Ihe curves shown in Fig. 3 of the drawing are similar tothe curves shown in Fig. 2 of the drawing and similar curves will bedesignated by like reference characters. Curve 44 may be considered torepresent thegplate voltage and the curve 46 may be considered torepresent a grid bias curve as in Fig. 2 of the drawing. A curve 50represents a critical grid voltage curve for a rectifier device in whichthe filament is connected in parallel and the grid return connectionmade to the mid-point of the filament transformer winding. The curve 45represents a critical grid voltage curve for a rectifier device in whichthe filament is connected in series as shown in Fig. 1 of the drawing.The difference between the critical voltage curves 45 and 50 isessentially onehalf the voltage drop across a filament of a rectifierdevice. voltage curve 45 over the critical grid voltage curve 50 isapparent by considering the intersection of the grid bias curve 46 withthe curve 45 at point :c and the intersection of a grid bias curve 55with the critical grid voltage curve 50 at point y. The points z and yare at the same point with respect to the abscissae and will ignite therectifier device at the same point. However, it will be noted that thegrid bias curve 46 The advantage of the critical grid Cil on the platesof the devices, and means for imof larger alternating current biasintersects the curve at a much sharper angle than the curve intersectsthe curve 50. The sharper the intersection between the grid bias curveand afcritical voltage curve, the more stable the operation of theregulator. Therefore,' it is desirable to have as large an alternatingcurrent bias on the grids as possible. By connecting the iilament of therectifier devices in series and polarizing them as before set forth, ahigher alternating current bias may be obtained.

Modifications yin the circuits and in the arrangement and location Iofparts may be made Within the spirit and scope of the invention and suchmodifications are intended to be covered by the appended claims.

What is claimed is:

1. In a rectiiier system, an alternating current supply circuit, adirect current load circuit, two gas-lilled space discharge devices,means for connecting said devices between said circuits to supply theload circuit with full wave rectifled current, means for impressingalternating current on the grids of said devices substantially 90degrees outof phase with the potential impressed pressingaI directcurrent bias on the grids of said devices according to the load circuitvoltage to control said devices and maintain the load circuit voltagesubstantially constant.

2. In a rectiiier system, an alternating current supply circuit, agas-filled space-discharge rectiiier device having a control grid, meansfor controlling said device by varying the potential on the gridthereof, said device being connected to said supply circuit, and aiilter comprising series andshunt impedance elements for connecting,said device to a load circuit, said illter having a series inductanceelement at its input end which has relatively small reactance to preventdelay in the rectifier cut-oil? and a condenser of relatively largecapacity serving as the output shunt element of the illter to preventquick changes in the load circuit voltage.

3. In a rectifler system, an alternating current supply circuit, arectifier space discharge device connected to said circuit and having acontrol grid, a iilter comprising series and shunt elements forconnecting said device to a load circuit, said iilter4 having a seriesinductance element at its input end which has a relatively smallreactance to prevent delay in the rectiiier cut-oi'and a storage elementof relatively large size serving as the output shunt element of theiilter to prevent sharp changes in the load circuit voltage, and meansfor varying the potential on the gridv of said device to maintain theload circuit voltage constant.

4. In a rectifier system, an alternating. current supply circuit, agas-lled space-discharge rectifier device having a control grid andconnected to said circuit, a iilter comprising series and shunt elementsfor connecting said device to a load circuit, said` iilterhaving aseries inductance element at its input end which has relatively smallreactance to prevent delay inthe rectifier cut-off and a condenser ofrelatively large capacity serving as the output shunt element of theiilter to prevent quick changes in the load cirf cuit voltage, and meansfor impressing an alternating current bias and a direct current bias onthe grid of said device and for varying the direct current biasaccording to the voltage of the load circuit to maintain the loadcircuit voltage constant.

anaaao 5. In a rectiiier system, a three-element space dischargerectifier connected between an alternating current supply circuit and adirect current load circuit, a resistance divided into sections andconnected across said load circuit, means comprising a space dischargeregulator device having a control grid for controlling the potentialbias on the rectifier grid to govern the load circuit voltage, meanscomprising a source of biasing potential connected in the grid circuitof the regulator device in opposition to the voltage across one sectionof said resistance for controlling the regulator device to maintain theload circuit voltage constant, and means for varying another section ofsaid resistance to govern the level at which the load circuit voltage ismalntained constant.

6. In a rectiiier system, a direct current load circuit, a source ofpotential for saidload circuit,

a resistance divided into sections and connected across said loadcircuit, a space discharge regulator device having the grid circuitthereof connected across one section of said resistance, a biasingpotential connected in the grid circuit of said regulator device inopposition to the potential drop across said section of resistance,means comprising a second space discharge device controlled by saidregulatory device for controlling said source to maintain the loadcircuit voltage substantially constant, and means for varying anothersection of said resistance to govern the level at which the load circuitvoltage is maintained constant.

7. In a rectifier system, an alternating current supply circuit, adirect current load circuit, a gas-filled space discharge rectiiierconnected between said circuits and having a control grid, an adjustabletransformer connected between said supply circuit and the rectiiier forcontrolling the potential impressed on the rectifier plate,-a reothersection of said resistance to govern they level at which the loadcircuit voltage is maintained constant and for simultaneously varyingsaid adjustable transformer to maintain an optimum potential on therectifier plate.

8. In a rectiiier system, a gas-filled space discharge device having acontrol grid, means for connecting said device between an alternatingcurrent supply circuit and a direct current load circuit, means forimpressing an alternating current bias on the grid of said device whichis out of phase with respect to the potential on the plate a constantamount, a resistance element connected across said load circuit, aregulating space discharge device having a control grid, a source ofnegative potential connected to the grid of the regulating device, meansfor connecting the grid circuit of said regulating device across saidresistance with the potential drop across the resistance elementopposing the negative bias impressed on the grid of the regulatingdevice, and means controlled by said regulating device for impressing anegative bias on the grid of said lll gas-filled device to maintain therectified voltage substantially constant.

9. In a rectifier system, a rectifier space discharge device having acontrol grid, means for connecting said device between an alternatingcurrent supply circuit and a direct current load circuit, means forimpressing an alternating current bias on the grid of said device whichis out of phase with respect to the potential on the plate a constantamount, a regulating space dis- `charge device, means for operating saidregulating device according to the voltage on said load circuit, andmeans controlled by said regulating device for impressing a directcurrent bias on the grid of said rectifier device to maintain therectified voltage substantially constant.

10. In a rectifier system, a gas-filled space discharge device having acontrol grid, means for connecting said device between an alternatingcurrent supply circuit and a load circuit to supply the load circuitwith rectified current, means for impressing an alternating current biason the grid of said device which is out of phase with respect to thepotential on th'e plate of the device a constant amount, an,impedancedivided into sections and connected across said load circuit, aregulating space discharge device having a control grid, a source ofnegative potential connected to the grid of the regulating device, meansfor connecting the grid circuit of said regulating device across asection of said impedance with the potential drop ofthe section inopposition to the negative bias impressed on the grid of the regulatingdevice and for obtaining plate potential for the regulating device froma number of said impedance sections, and means controlled by saidregulating device for impressing a negative bias on the grid of saidgas-filled device to maintain the rectified voltage substantiallyconstant.

11. In a rectifier system, an alternating cur rent supply circuit, adirect current load circuit, two gas-filled space discharge rectifiershaving control grids, means for connecting said rectifiers between thesupply circuit and the load circuit to supply the load circuit with fullwave rectified current, means for connecting the filaments of saidrectifiers in series relation to the alternating current supply circuitwith the grid return terminal connected between the series connectedlaments and with the filament terminal opposite the grid return terminalof each filament polarized oppositely to the associated anode toincrease the critical external grid voltage, and means for impressing analternating current and a direct current bias on the grids of saidrectifiers.

12. In a rectifier system, an alternating current supply circuit, adirect current load circuit, two three-element gas-filled rectifiers,means for connecting said rectiiiers oppositely between the supplycircuit and the load circuit to supply the load circuit with full waverectifier current, means for connecting the filaments of tsaidrectifiers in series relation to the alternating current supply circuit,the grid return terminal being connected between the series connectedfilaments and the filament terminal opposite the grid return terminal ofeach filament being polarized oppositely to the associated anode toincrease the critical external grid voltage, means for impressing analternating potential on the grids of said rectifiers out of phase withrespect to the anode potentials a constant amount, and means forimpressing a direct current bias on the grids of said rectifiers whichvaries according to the voltage of the load circuit.

13. In a rectifier system, .a three-element gasfilled rectifierconnected between an alternating current supply circuit and a directcurrent load circuit, means for impressing an alternating potential onthe grid of said rectifier which is out of phase with respect to theanode potential a constant amount, means for impressing a direct currentbias on the grid of said rectifier which varies according to the loadcircuit voltage, and means for connecting the filament of said rectiv erto the alternating current supply circuit with the filament terminalspolarized so that the filament terminal opposite to the grid returnterminal is polarized oppositely to the anode of the rectifier.

14. In a rectifier system, a three-element gasiilled rectifier connectedbetween an alternating current supply circuit and a direct current loadcircuit, means for impressing an alternating potential on the grid ofsaid rectifier which is out of phase with respect to the anode potentiala constant amount, means for impressing a direct current bias on thegrid of said rectifier which varies according to the load circuitvoltage, and means for energizing the filament of said rectifier withalternating potential and for effecting polarization of the filamentterminals with respect to the anode potential so that the voltage dropacross the filament is added to the critical external grid voltage.

15. In a rectifier system, a three element gasfllled rectifier connectedbetween an alternating current supply circuit and a direct current loadcircuit, means for impressing an alternating potential on the grid ofsaid rectifier which is out of phase with respect to the anode potentiala constant amount, means for impressing a direct current bias on thegrid of said rectifier which varies according to the load circuitvoltage, and means for energizing the filament of said recti- `fier withthe filament terminals polarized so that the filament terminal oppositeto the grid return terminal is polarized oppositely to the anode of therectifier.

JAMES R. POWER.

